Resin molded product having metallic luster surface

ABSTRACT

A resin molded product having a metallic luster surface is provided without performing harmful chromium plating. The resin molded product  1  is constituted of a transparent sheet  2,  a metallic luster layer  3  formed on a backside of this transparent sheet  2,  and a synthetic resin  4  integrally molded on a backside of this metallic luster layer  3.  The transparent sheet  2  consists of a sheet having heat resistance, such as polycarbonate having transparency, polyester sheet, etc. The metallic luster layer  3  is a metal vacuum evaporated layer formed by vacuum evaporation on a backside of the transparent sheet  2,  or a printed layer formed by printing using a mirror ink.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a resin molded product having a metallic luster surface.

[0003] 2. Description of the Related Art

[0004] Chromium plating has been performed in order to give metallic luster to a surface of conventional and various products.

SUMMARY OF THE INVENTION

[0005] However, chromium used in chromium plating is harmful, and has a possibility of becoming a cause of environmental pollution, and simultaneously of injuring operator's health.

[0006] Therefore, an object of the present invention is to provide a resin molded product having a metallic luster surface, without performing harmful chromium plating having possible disadvantage, such as cause of environmental pollution.

[0007] In order to solve the above described problems, in a resin molded product having a metallic luster surface by the present invention, the metallic luster layer consisting of a metal vacuum evaporated layer is formed on a backside of a transparent sheet, and then a synthetic resin is integrally formed onto the above described backside of the sheet in which this metallic luster layer is formed. In this case, metal vacuum evaporation may be directly performed onto the backside of the transparent sheet to form a metallic luster layer consisting of metal vacuum evaporated layer, or metal vacuum evaporation is performed on a separately prepared release sheet to form a separable metal vacuum evaporated layer on this release sheet, and then this metal vacuum evaporated layer may be adhered to a backside of the above described transparent sheet, and, subsequently the above described release sheet may be removed. When such a process is adopted, in order to increase adhesiveness between the metal vacuum evaporated layer surface and the backside of the above described transparent sheet, it is preferable that heat fusible binder is beforehand coated on the surface of the metal vacuum evaporated layer, and then the metal vacuum evaporated layer is adhered by pressure with heat to the above described backside of the transparent sheet.

[0008] Thus, if a synthetic resin is integrally formed on a backside of a transparent sheet with which metallic luster layer is formed in a backside, the metallic luster layer of the backside is viewed through the transparent sheet, and a feeling of beauty as if metal plating is completely performed is shown, when the resin molded product concerned is observed from outside.

[0009] Moreover, in the present invention, a metallic luster layer is formed by printing using a mirror ink on a backside of a transparent sheet, and a synthetic resin is integrally formed on the above described backside of this sheet on which this metallic luster layer is formed. Therefore when the resin molded product concerned is observed from outside, the metallic luster layer of the backside is viewed through a transparent sheet, and a feeling of beauty as if metal plating is performed is shown.

[0010] Moreover, the above described metallic luster layer formed by printing in the present invention is a printed layer by a mirror ink including pieces of aluminum foil having a thickness of no more than 0.5 μm, preferably of no more than 0.25 μm, and more preferably of no more than 0.05 μm as a principal component of foil. Therefore, in the present invention, a mirror ink is an ink including pieces of aluminum foil having a thickness of no more than 0.5 μm, preferably of no more than 0.25 μm, and more preferably of no more than 0.05 μm as a principal component of foil.

[0011] If a thickness of aluminum foil to be used is thick exceeding 0.5 μm, specular surface luster equivalent to metal plating will not be given on the surface of resin molded product.

[0012] In addition, aluminum foil to be used preferably has pieces of aluminum foil having foil area of 10 μm² to 2000 μm² as a principal component. In order to obtain a foil area, fully diluted ink is observed under microscope, and image analysis of area of the observed piece of foil is carried out to determine an area of piece of foil. Therefore, an area of piece of foil represents an area of one of the two surfaces of the piece of foil here. When there are many pieces of foil having a foil area of no more than 10 μm², advanced specular luster may not be obtained. Moreover, when there are many pieces of foil having no less than 2000 μm² of foil area, streaks and uneven prints will be easily given in printing of screen-stencil, gravure, flexographic printing, etc. Therefore, a foil area of foil principal component of aluminum foil used for the present invention is preferably 10 μm² to 2000 μm², and more preferably 10 μm² to 1500 μm².

[0013] Moreover, in a resin molded product having a metallic luster surface of the present invention, a sheet on which the above described metallic luster layer is formed by printing of mirror ink is shaped, and the above described synthetic resin is integrally formed on the above described backside. That is, when a resin molded product has various surface configurations, the transparent sheet on which metallic luster layer is formed is firstly shaped to the surface configuration concerned.

[0014] Since the above described metallic luster layer is a printed layer by a mirror ink including pieces of the above described aluminum foil as a foil principal component at this time, very thin pieces of aluminum foil piles repeatedly without any space among them to constitute this printed layer. Therefore, even if the transparent sheet is extended by shaping and the metallic luster layer is also extended in connection with shaping, although pieces of aluminum foil in a section where the metallic luster layer concerned is extended is moved in an extended direction, any space will not be formed among laps of pieces of aluminum foil. Therefore, either crack or fracture of metallic luster layer are hardly formed in the extended section, and a shaped resin molded product having a metallic luster layer that has neither crack nor fracture may be provided.

[0015] In order to easily perform the above described shaping, it is common to soften the transparent sheet printed by a mirror ink with heat, and to perform shaping by press forming, vacuum forming, pressurized-air forming, etc.

[0016] Moreover, a synthetic resin is preferably formed integrally by insert molding on the above described backside of a sheet on which metallic luster layer is formed.

[0017] Moreover, in the present invention, a middle resin layer is further prepared between the above described metallic luster layer and the above described integrally molded synthetic resin. Operational advantages of following (1) and (2) will be demonstrated by preparing this middle resin layer.

[0018] (1) When a synthetic resin heated and melted at elevated temperature is integrally molded by insertion molding etc. on the above described backside of a sheet with which a metallic luster layer is formed, this middle resin layer may prevent that the mirror ink layer forming the metallic luster layer is melted and moved by the heat and flow of the injected resin and reduces luster, or that heat deformation gives damage to the metallic luster layer.

[0019] (2) Adhesive strength between the metallic luster layer and the synthetic resin integrally molded will be improved by the middle resin layer.

[0020] Moreover, above described middle resin layer comprises one layer or two or more layers. In case of two or more layers, it may comprise two layers. In this case, the first layer (the layer that touches ametallic luster layer) is preferably a layer consisting of a partially cross-linked thermoplastic resin. The second layer (the layer that touches an integrally molded synthetic resin) is preferably a layer consisting of a thermoplastic resin without cross-link or, with a degree of cross-link lower than the first layer.

[0021] In addition, the middle resin layer may include pigments etc.

[0022] Moreover, in the present invention, as a method of preparing a middle resin layer, a method is commonly used in which a metallic luster layer is formed on a backside of a transparent sheet, and furthermore an ink or a coating agent including a resin component and/or a cross-linking agent, etc. constituting a middle resin layer is printed or coated on the layer.

BRIEF DESCRIPTION OF THE DRAWINGS

[0023]FIG. 1 is sectional view showing the first embodiment of the present invention;

[0024]FIG. 2 is sectional view showing the second embodiment of the present invention;

[0025]FIG. 3 is a sectional view showing the third embodiment of the present invention; and

[0026]FIG. 4 is a sectional view showing the fourth embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] Hereinafter, embodiments of the present invention will be described with reference to figures.

[0028] (The First Embodiment)

[0029] As is shown in FIG. 1, a resin molded product 11 concerning First Embodiment of the present invention is constituted of a transparent sheet 2, a metallic luster layer 3 formed on a backside of this transparent sheet 2, a middle resin layer 6 laminated onto a backside of this metallic luster layer 3, and a synthetic resin 4 integrally molded onto a backside of this middle resin layer 6. The transparent sheet 2 consists of a sheet of polycarbonate, polyester sheet etc. having transparency and heat resistance. A metallic luster layer 3 is a layer formed by a method in which a metal is directly vacuum evaporated to a backside of a transparent sheet 2, or a layer that is prepared by a method in which metal vacuum evaporation is performed on a release sheet currently prepared separately, heat welding binder is coated on a separable metal vacuum evaporated layer formed on this release sheet, and then the coated layer is adhered to a backside of the above described transparent sheet with heat and peeled off the release sheet. In order to protect the backside of the above described metal vacuum evaporated layer, full surface printing is given by a polyester ink to form a middle resin layer 6.

[0030] Thereby, appearance of surface of the transparent sheet 2 has advanced specular luster. Next, ametallic luster sheet 5 with which a metallic luster layer 3 and a middle resin layer 6 are thus formed on a backside of the transparent sheet 2 is set in a metal mold with a backside having the middle resin layer 6 being faced inside, subsequently, a synthetic resin melted with heat is injected into the above described metal mold, and after the synthetic resin 4 solidified, the mold is opened. Thus, molding of illustrated resin molded product 11 is completed.

[0031] When the resin molded product 11 concerned is observed from outside, the metallic luster layer 3 on the backside is viewed through the transparent sheet 2, and feeling of beauty as if metal plating is performed is shown. Therefore, a resin molded product 11 having a metallic luster surface is obtained, without harmful chromium plating having disadvantage, such as cause of environmental pollution.

[0032] (The Second Embodiment)

[0033]FIG. 2 shows a resin molded product 21 concerning Second Embodiment of the present invention. This resin molded product 21 is constituted of a transparent sheet 2, a metallic luster layer 3 formed on a backside of this transparent sheet 2, and a synthetic resin 4 integrally molded in a backside of this metallic luster layer 3. The transparent sheet 2 consists of a sheet of polycarbonate, polyester sheet etc. having transparency and heat resistance. A metallic luster layer 3 is a printed layer currently formed on a backside of the transparent sheet 2 by printing using a mirror ink A or a mirror ink B comprising a following components.

[0034] Mirror ink A; aluminum foil having pieces of aluminum foil with a thickness of 0.25 μm and a foil area of 20 to 2000 μm² as a principal component 100 parts by weight, polyester resin 40 parts by weight, ester based solvent 800 parts by weight, and ketone based solvent 500 parts by weight.

[0035] Mirror ink B; aluminum foil having pieces of aluminum foil with a thickness of 0.03 μm and a foil area of 10 to 2000 μm² as a principal component 100 parts by weight, polyurethane resin 55 parts by weight, cellulose derivatives 10 parts by weight, and ester based solvent 1500 parts by weight.

[0036] This resin molded product 21 is manufactured by a method for production comprising following processes. That is, the above described mirror ink A or B is used, and gravure or screen-printing is given onto a backside of the transparent sheet 2. Thereby, a metallic luster layer 3 is formed on the backside of the transparent sheet 2, and appearance of the surface of the transparent sheet 2 has advanced specular luster.

[0037] Then, a metallic luster sheet 5 in which the metallic luster layer 3 is formed on the backside of the transparent sheet 2 is shaped into a form having a circular convex portion 5 a in a central section viewed from upper direction by a vacuum forming, a pressurized-air forming, etc. as is shown in FIG. 2. Since the above described metallic luster layer 3 is a printed layer by a mirror ink including pieces of the above described aluminum foil as a principal foil component, flakes of aluminum foil pile to constitute this printed layer. Therefore, when the transparent sheet 2 is extended in rising section Q1 and Q2 by shaping, and the metallic luster layer 3 is extended in connection with the rising, metallic luster similar to specular surface of a section where the metallic luster layer concerned is extended will not be lost. Moreover, in curved portions P1, P2, P3, and P4, neither crack nor fracture appears in a metallic luster layer.

[0038] Furthermore, this shaped metallic luster sheet 5 is set into a metal mold with the backside having metallic luster layer 3 faced inside, and subsequently a synthetic resin melted with heat is injected into the above described metal mold, and the mold is opened after the synthetic resin 4 being solidified. Thereby, as illustrated, molding of a resin molded product 21 having convex portion 5 a in a central section is completed.

[0039] When this resin molded product 21 is observed from outside, metallic luster is observed on whole area of the resin molded product through the transparent sheet 2, neither crack nor fracture is observed also in portions P1, P2, P3, and P4, and feeling of beauty as if metal plating is performed is shown. Therefore, a resin molded product 21 having a metallic luster surface is obtained, without harmful chromium plating having disadvantage, such as cause of environmental pollution.

[0040] (The Third Embodiment)

[0041]FIG. 3 shows a resin molded product 31 concerning the Third Embodiment of the present invention. This resin molded product 31 is constituted of a transparent sheet 2, a metallic luster layer 3 formed on a backside of this transparent sheet 2, a middle resin layer 6 laminated onto a backside of this metallic luster layer 3, and a synthetic resin 4 integrally molded on a backside of this middle resin layer 6. The middle resin layer 6 consists of a partially cross-linked thermoplastic resin having polyester resin as a principal component.

[0042] This resin molded product 31 is manufactured by a method of production comprising following processes. That is, printing is given to a transparent sheet 2 on a backside using the mirror ink A and B mentioned above to form a metallic luster layer 3. Furthermore, printing is given on the metallic luster layer 3, using an ink consisting of a polyester resin and a little amount of cross-linking agent to form a middle resin layer 6.

[0043] Then, a metallic luster sheet 5 in which the metallic luster layer 3 and the middle resin layer 6 are formed on the backside of the transparent sheet 2 is shaped into a form having convex portion 5 a in a central section, as illustrated, by vacuum forming, pressurized-air forming, etc. At this time, neither crack nor fracture is formed in the above described sections Q1, Q2, P1, P2, P3, and P4 (refer to FIG. 2) of the metallic luster layer 3 as described above.

[0044] Furthermore, this shaped metallic luster sheet 5 is set in a metal mold so that a backside having a middle resin layer 6 may face inside, and subsequently a synthetic resin melted with heat at an elevated temperature is injected into the above described metal mold. At this time, direct contact between the injected resin melted at an elevated temperature and the metallic luster layers 3 are blocked by the middle resin layer 6. Thereby, the mirror ink that forms the metallic luster layer 3 is not melted nor moved by heat and flow of the injected resin, and as a result disadvantage of luster decrease may be prevented.

[0045] And when the injected synthetic resin 4 is solidified, the synthetic resin 4 will be firmly integrated by the middle resin layer 6 with the transparent sheet 2 on which the metallic luster layer 3 is formed. The mold is subsequently opened, and as illustrated, a resin molded product 31 having convex portion 5 a in a central section and a metallic luster surface will be obtained.

[0046] (The Fourth Embodiment)

[0047]FIG. 4 shows a resin molded product 41 concerning the Fourth Embodiment of the present invention. This resin molded product 41 is constituted of a transparent sheet 2, a metallic luster layer 3 formed in a backside of this transparent sheet 2, a first middle resin layer 7 laminated to a backside of this metallic luster layer 3, a second middle resin layer 8 integrally formed on a backside of this first middle resin layer 7, and a synthetic resin 4 integrally molded on a backside of this second middle resin layer 8.

[0048] The first middle resin layer 7 consists of a partially cross-linked thermoplastic resin. The second middle resin layer 8 consists of a thermoplastic resin without cross-linking, or with a degree of cross-link lower than the first middle resin layer 7.

[0049] This resin molded product 41 is manufactured by a method for production consisting of following processes. That is, a similar mirror ink mentioned above is used, printing is given to a backside of the transparent sheet 2 to form the metallic luster layer 3. Then, printing is given on the metallic luster layer 3 to form the first middle resin layer 7 using an ink including a polyester resin and a cross-linking agent. Furthermore, printing is given on the first middle resin layer 7, using, for example, a resin without cross-linking like vinyl chloride-vinyl acetate copolymer, or a thermoplastic resin including cross-linking agents fewer than the first middle resin layer 7 as ink to form the second middle resin layer 8.

[0050] Then, a metallic luster sheet 5 in which the metallic luster layer 3, the first middle resin layer 7, and the second middle resin layer 8 are formed on a backside of the transparent sheet 2 is shaped into an illustrated form having convex portion 5 a in a central section by vacuum forming, pressurized-air forming, etc. At this time, neither crack nor fracture appears in the above described sections Q1, Q2, P1, P2, P3, and P4 of the metallic luster layer 3 (refer to FIG. 2) as described above.

[0051] Furthermore, this shaped metallic luster sheet 5 is set into a metal mold with the backside of the second middle resin layer 8 being faced inside, and subsequently a synthetic resin melted by heat at an elevated temperature is injected into the above described metal mold. At this time, direct contact between the injected melted resin at an elevated temperature and the metallic luster layer 3 is prevented by the first, and second middle resin layers 7 and 8. Thereby, a mirror ink that forms the metallic luster layer 3 is not melted nor moved by the heat and flow of the injected resin, and as a result disadvantage of luster decrease may be prevented.

[0052] And when the injected synthetic resin 4 is solidified, the synthetic resin 4 will be bonded to the second middle resin layer 8, and firmly integrated by the first and second middle resin layers 7 and 8 with the transparent sheet 2 on which the metallic luster layer 3 is formed. The mold is subsequently opened, and as illustrated, a resin molded product 41 having convex portion 5 a in a central section and a metallic luster surface will be obtained. This molded product showed a very strong bond strength between the metallic luster sheet and the synthetic resin 4.

[0053] In addition, although molded products having convex position 5 a in a central section are shown as resin molded products 21, 31, and 41 in the embodiments it is clear that the present invention may be applied also in molded products having more complicated concavo-convex forms etc., or flat-shaped resin molded products.

[0054] As described above, adopting the present invention, a resin molded product having a metallic luster surface or advanced specular luster and showing feeling of beauty as if metal plating is performed can be provided, without performing plating using chromium that has a possibility of causing environmental pollution and injuring operator's health. 

What is claimed is:
 1. A resin molded product having a metallic luster surface, wherein a metallic luster layer consisting of a vacuum deposited metal layer is formed on a backside of a transparent sheet, and a synthetic resin is integrally formed on said backside of a sheet having the metallic luster layer formed thereon.
 2. A resin molded product having a metallic luster surface, wherein a metallic luster layer is formed on a back side of a transparent sheet by printing using a mirror ink, and a synthetic resin is integrally formed on said back side of a sheet having the metallic luster layer formed thereon.
 3. The resin molded product having ametallic luster surface according to claim 2, wherein said metallic luster layer is a printed layer by a mirror ink including pieces of aluminum foil having a thickness of no more than 0.5 μm as a foil principal component.
 4. The resin molded product having a metallic luster surface according to claim 2, wherein said sheet having a metallic luster layer formed thereon is shaped, and said synthetic resin is integrally formed on said backside.
 5. The resin molded product having a metallic luster surface according to claim 3, wherein said sheet having a metallic luster layer formed thereon is shaped, and said synthetic resin is integrally formed on said backside.
 6. The resin molded product having a metallic luster surface according to any one of claims 1 to 5, wherein said synthetic resin is molded by insertion molding method.
 7. The resin molded product having a metallic luster surface according to any one of claims 1 to 5, wherein a middle resin layer is further prepared between said metallic luster layer and said synthetic resin integrally molded.
 8. The resin molded product having a metallic luster surface according to claim 6, wherein a middle resin layer is further prepared between said metallic luster layer and said synthetic resin integrally molded. 